docs: def bind(self, fn: Callable[[Any], 'Observable']) -> 'Observable':
          r"""Chain continuation passing functions.
  
          Haskell: m >>= k = Cont $ \c -> runCont m $ \a -> runCont (k a) c
          """
          source = self
          return Observable(lambda on_next: source.subscribe(lambda a: fn(a).subscribe(on_next)))